Data Set Summary

This data set includes daily, monthly, and yearly mean surface air temperatures for four interior West Antarctic sites between 1978 and 1997. Data include air surface temperatures measured at the Byrd, Lettau, Lynn, and Siple Station automatic weather stations. In addition, because weather stations in Antarctica are difficult to maintain, and resulting multi-decade records are often incomplete, the investigators also calculated surface temperatures from satellite passive microwave brightness temperatures. Calibration of 37-GHz vertically-polarized brightness temperature data during periods of known air temperature, using emissivity modeling, allowed the investigators to replace data gaps with calibrated brightness temperatures.

MS Excel data files and GIF images derived from the data are available via ftp from the National Snow and Ice Data Center.

Different coverages are available for each site. The Siple Station and Byrd records begin 25 October 1978, the Lettau record begins 1 January 1986, and the Lynn record begins 10 July 1987. All records end 31 December 1997.

AWS data were obtained from 3-hourly files on the anonymous FTP site operated by the University of Wisconsin (ftp://ice.ssec.wisc.edu/pub/). The investigators derived daily average values for comparison with brightness temperatures (see below). Information about the AWS units used for air temperature measurements is available at the Antarctic Automatic Weather Stations Project Web site, and is also provided by Stearns et al. (1993) and Stearns and Weidner (1993).

Because weather stations in Antarctica are difficult to maintain, and resulting multi-decade records are often incomplete, the investigators also calculated surface temperatures from satellite passive microwave brightness temperatures (Tbs). Tbs are functions of many characteristics of the surfaces they describe. In areas covered by dry snow, Tbs effectively represent the physical temperature of the near-surface snow, mulitiplied by its emissivity. Thus Tbs cannot be directly substituted for missing AWS temperature measurements, but must first be calibrated to account for variations in snow emissivity.

To create this data set, the investigators compiled daily-averaged, vertically-polarized 37-GHz Tbs from the Scanning Multichannel Microwave Radiometer (SSMR) and Special Sensor Microwave/Imager (SSM/I; see NSIDC's DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures). Brightness temperatures were then compared with temporally equivalent near-surface air temperatures (measured by AWS) to calculate emissivity. Modeled emissivity time series were then used to convert the longer, continuous Tb records into calibrated near-surface air temperatures. Please consult Shuman and Stearns (2001) for more information.